Foals raised on pasture with or without daily pyrantel tartrate feed additive: comparison of parasite burdens and host responses following experimental challenge with large and small strongyle larvae.
Three groups of foals were raised under different management programs in this study: Group 1 (n = 6) and Group 2 (n = 6) were raised with their dams on pasture; Group 3 foals (n = 5) were raised under parasite-free conditions. Mares and foals of Group 1 received daily pyrantel tartrate (PT) treatment with their pelleted feed ration, whereas mares and foals of Groups 2 and 3 received only the pelleted ration. Pasture-reared foals were weaned and moved to a heavily contaminated pasture for 5 weeks. Group 1 foals continued to receive daily PT treatment whereas Group 2 foals received only the pelleted feed ration. Following this period, all foals were moved into box stalls. Half of each group was challenged with 10(3) Strongylus vulgaris infective third-stage larvae (L3), 5 x 10(3) Strongylus edentatus L3 and 10(5) mixed cyathostome L3; the remaining half served as unchallenged controls. Necropsy examinations were performed 6-week post-challenge for evaluation of parasite burdens and lesions. Daily PT treatment of Group 1 reduced the patent cyathostome infections of both mares and foals and was effective in reducing pasture burdens of infective larvae. Daily treatment of Group 1 foals during weaning continued to suppress EPG levels; however, it did not prevent large strongyle infections during the weaning period. Group 1 foals were more sensitive to challenge than Group 2 foals, which did not exhibit any post-challenge disturbances. Group 1 foals were equally susceptible to challenge as parasite-free foals.
Monahan
C M
CM
Department of Veterinary Microbiology and Parasitology, School of Veterinary Medicine, Louisiana State University, Baton Rouge 70803, USA.
Chapman
M R
MR
Taylor
H W
HW
French
D D
DD
Klei
T R
TR
D000821:Animal Feed; D000818:Animals; D000969:Antinematodal Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D005243:Feces / Q000469:parasitology; D005260:Female; D005503:Food Additives; D006734:Horse Diseases; D006736:Horses / Q000469:parasitology*; D007413:Intestinal Mucosa / Q000469:parasitology*; D007559:Ivermectin / Q000627:therapeutic use; D007814:Larva; D010270:Parasite Egg Count / Q000662:veterinary; D010271:Parasites / Q000145:classification / Q000302:isolation & purification; D006109:Poaceae; D011247:Pregnancy; D011715:Pyrantel / Q000008:administration & dosage / Q000627:therapeutic use*; D017206:Strongylida Infections / Q000517:prevention & control / Q000662:veterinary*; D013323:Strongylus
D000969:Antinematodal Agents; D005503:Food Additives; D011715:Pyrantel; D007559:Ivermectin